1. Field of the Invention
The present invention relates in general to the field of wall coverings and in particular to the field of decorative wall coverings which are primarily intended to be used outdoors and function to protect the base wall from the deteriorating effects of the elements of nature.
2. Description of the Prior Art
Providing a plain wall surface with an aesthetically-pleasing covering has been a long time goal of man. Further, providing such a decorative wall covering in an environment whereby the wall and the covering are exposed to the harsh elements of nature has also been a long time goal and one which is obviously much more difficult to attain than where the wall covering is, for example, used indoors. The problem is even more complicated when an added requirement comprises protecting the base wall from the deteriorating effects of the environment. Still today, the search for such wall coverings continues. The myriad number of natural and synthetic wall coverings in use today is a tribute to this long-standing search. Yet, even with today's so-called space age materials, a fully satisfactory solution to the problem has yet to be attained. The present invention, however, comprises a wall covering which is both decorative and useful and overcomes many of the prior art problems in this field.
The prior art is primarily exemplified by U.S. Pat. No. 4,522,002, which patent comprises our prior efforts to overcome the above-stated prior art problems. In that patent, we previously addressed the state of the then prior art and the various attempts to overcome the problems of proper installation while providing for expansion and contraction of the panels due to changes in the temperature. For example, it was previously stated that overcoming the effects of thermal expansion of the panels is a critical factor in providing a wall panel because panels will expand as much as five-eighths of an inch over a forty-inch length of panel at temperatures of 160.degree. Fahrenheit. Such temperatures are easily attained on hot, sunny days because, in part, of the heat-sink and hot house effect of panels covering a surface such as a wall or a roof and which are spaced from said wall or roof by a discrete distance leaving a stagnant air space therebetween. Also as previously explained, various types of expanding joints have been built into the panels so that the panels can expand without buckling away from the walls on which the panels are mounted. Generally, in the prior art, expandable tongue-and-groove joints were used in conjunction with breakable pins. The pins are provided for purposes of installation which functions as a stop between panels when adjacent panels are mounted to the wall during installation. Then, when subject to thermal expansion, the pins are allowed to break and the tongue is allowed to further engage within its associated groove. This system of interlocking panels, as explained, suffered from loose tongue and grooves which allowed rattling of the panels after installation and, for example, when subject to even mild wind conditions.
Accordingly, our previous U.S. Pat. No. 4,522,002, particularly addressed the problem of thermal expansion. Our previous patent materially overcame many of the prior art problems and represents a significant improvement in the state of the art of decorative all panels. One aspect of our prior patent comprised the contribution of utilizing a material made of polypropylene with twenty percent (20%) calcium carbonate filler which composition of matter significantly decreased the thermal co-efficient of expansion and contraction as compared to prior art materials. Another aspect of our prior patent comprised providing flexible pins to bear on a tongue in a tongue-and-groove interlock as regards horizontal expansion joints and the tongue-and-groove interlock in combination with ramping surfaces for a bendable flange to slide over and bear on for vertical expansion joints which combination was substantially tight and rattle free under prevailing outdoor conditions.
There are times, however, when severe wind and rain occur together which causes the rain to accelerate and thereby penetrate further than normal. Under these adverse conditions, the wind causes slight lifting of the bottom horizontal edge of the decorative wall panels and allows the penetrating rain to enter underneath the wall panel and become trapped in the space between it and the wall. Once water enters this stagnant air space, it is very difficult to drive the moisture therefrom. Accordingly, an object of the present invention is to provide a decorative wall panel which prevents water from entering underneath the horizontal lower edge and forming a high humidity condition within the stagnant air space between the wall panel and the wall.
Another object of the present invention is to provide a decorative wall panel which prevents wind from lifting and water from entering the vertical joint between adjacent panels.
Another object of the invention include providing a decorative wall covering which allows for easy and foolproof installation whereby horizontal and vertical alignment between panels is easily attained and maintained.
Another object of the present invention is to provide a decorative wall panel which allows for both horizontal and vertical contraction and expansion while maintaining the aforesaid moisture barrier between adjacent panels.